Pigeonpea (Cajanus cajan L.) is a pigeon pea plants (Leguminosae sp), with a wide range of medicinal value. Main function of pigeonpea seeds is the treatment of liver and kidney edema, blood strangury, hemorrhoids leading to hematockezia, etc. Pigeon pea root has the functions of detoxification, removing dampness, and hemostasis, acesodyne, as well as disinsection, mainl used for the treatment of sore throat, hemorrhoids leading to hematockezia, blood strangury and edema, dysuria and so on. Pigeon pea leaves have the function of detoxification and detumescence, mainly used for the treatment of pediatric chickenpox, ulcers and so on. Pigeon pea leaves contain large amounts of stilbene-type compounds, such as cajanine, cajanine A, cajanine C (chemical structure shown in FIG. 1), these compounds have a wide range of pharmacological effects, such as anti-osteoporosis. Stilbene-type extracts, can effectively promote bone cell formation and inhibitbone cell absorption (Refer to Pharmaceutical Journal, 2007, 42 (4): 386-391). In the treatment of hyperlipidemia, stilbene-type extract from pigeon pea leavesis demonstrated to significantly lower abnormally elevated serum levels of TC, TG and LDL-C levels (see CN101204418A, 2008.6.25.). In addition, stilbene-type extract from pigeon pea leaves also has anti-hypoxic ischemic brain damage, it has the protection effect on the stability of brain microvascular membranes and brain cell membranes under cerebral ischemic conditions (Refer to Traditional Chinese Drug Research & Clinical Pharmacology, 2006, 17 (3): 172-174).
American scholars (see David C. Hopp et al. US20020058707 A1) also studied the hypoglycemic effect of structure analogous compounds of cajanine, cajanine A, and C, etc. (FIG. 1), the results showed that these compounds had good hypoglycemic effect, yet side effects were all small. The anti-inflammatory and analgesic effects of pigeon pea crude extract has also been demonstrated experimentally (see Sun shaomei et al., Chinese herbs, 1995, 26 (3:147-148), the experimental results showed that the cajanine preparation experimental samples had significant anti-inflammatory effect stronger than salicylic acid, and the effect was in a dose-dependent manner as well. Cajanine preparation significantly reduced vascular permeability compared with the control: inhibition rate of cajanine preparations was 38.96%. Moreover, study on the effect of cajanine preparation on the pain threshold in mice showed that, compared with that of the mice prior to administration, both by drenching high- and low doses of cajanine formulations (200, 120 mg/kg), the prolongation of the threshold was shown to extend more than twice, indicating that cajanine preparation had significant analgesic effect.
Results of the research on pharmacological effects of natural products showed cajanine and stilbene extracts from pigeon pea leaves had extensive pharmacological effect on a variety of human diseases with a strong pharmacological activity (such as osteoporosis, hyperglycemia, hyperlipoidemia, inflammation, tumors). In particular, they were shown to have a function of regulating mechanism on the balance of bone metabolism similar to estrogen (to promote bone formation while inhibiting bone resorption), and their toxic side effect were low, these studies are more in-depth in China.
However, the current domestic and international chemical researches concerning pigeonpea stilbene compounds are still limited to the natural medicinal chemistry level, such as: extraction of natural products, their isolation and structural identification. The number of the resulting structures of analogous compounds with definitely known structures is very limited. Moreover, owing to the restricted source of the related drugs, in-depth study of the pharmacological effects of natural product cajanine is difficult to develop. The inventor of this patent applied No. 201010256856.7 patent in China, was the first to complete the total synthesis of cajanine and cajanine A, thereby providing the chemical means and laying foundation for further expanding the diversity of the molecular structures of this type of compounds.